JPH04241362A - Toner for electrophotography - Google Patents

Abstract

PURPOSE:To improve electrostatic chargeability as well as to obtain an image having a fine color tone, superior color reproducibility, image retentivity and color transparency by incorporating a specified dye and carrying out coloring with this dye. CONSTITUTION:C.I. Disperse Blue 87 and/or a deriv. thereof is incorporated as a dye into a toner and this toner is colored with the dye. In order to color the toner, the dye and resin particles are dispersed in an aq. medium and treated at a prescribed temp. In this dispersion dyeing method, the treating temp. is preferably above the glass transition temp. of the resin by about 40 deg.C. The amt. of the resin particles dispersed in the aq. medium is preferably regulated to >=20wt.% of the amt. of the resulting aq. dispersion so as to increase dyeing efficiency.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic toner used as a developer in electrophotographic copying machines, laser printers, and the like. More specifically, the present invention relates to process color toners used for forming color images, and particularly to toners colored blue.

0002

[Prior Art] Electrophotography generally refers to photoconductive materials (often processed into a drum shape) made of inorganic materials such as selenium, amorphous silicon, and zinc oxide, or organic materials such as diazo compounds and pigments. (Photosensitive drum) is first uniformly charged, then irradiated with image-modulated light to form an electrostatic latent image, and developed by attaching powder to the electrostatic latent image using electrostatic force. After the powder is transferred onto a base material such as paper or film, if necessary, it is fixed by applying pressure, heating, or the like. Electrophotographic methods are currently widely used in copying machines, laser printers, and the like. In electrophotography, a powder that develops an electrostatic latent image on a photosensitive drum and is ultimately transferred to a base material such as paper or film to form an image is called a toner. These toners are usually mixed with carrier particles (carrier) such as iron powder or ferrite and used as a so-called developer. Color toners used to form color images generally have predetermined tones called process colors,
That is, toners colored in the three subtractive primary colors of yellow, magenta, and cyan are used. Conventionally, toners used in electrophotographic developers are produced by adding colorants, charge control agents, fluidity modifiers, grinding aids, etc. to thermoplastic resins, kneading them, pulverizing them, and then classifying them. Particles made by this method have been used. As a method for coloring electrophotographic toner using these pulverization methods, a method in which a coloring material is kneaded with a resin and then pulverized is mainly used. When a resin and a coloring material are kneaded in advance before pulverization, the coloring material needs to withstand the high temperatures during kneading with the resin. Since many dyes change color or fade depending on the temperature during kneading, the usable coloring materials are limited to pigments.

0003

[Problems to be Solved by the Invention] Conventionally known inorganic pigments have many safety and health problems, and as a practical matter, it is difficult to use toners containing these in general copiers, printers, etc. It's impossible. Some organic pigments also have safety and health problems, and the ones that can actually be used as coloring materials are limited. Even if there are no health and safety issues, there are many that have problems with image retention. That is, many organic coloring materials undergo discoloration and fading due to exposure to ultraviolet rays, and there are few that are particularly satisfactory in terms of color image retention. When coloring with pigments, the coloring material is merely dispersed in the binder resin of the toner, resulting in poor transparency. Therefore, the color reproducibility when a plurality of colors are overlapped is insufficient, and the reproduction range of intermediate colors becomes narrow. Further, the influence of transparency is particularly noticeable when an image is formed on a transparent sheet for an overhead projector. In other words, because the transparency of the toner layer is poor, the projected image has a dim and muddy tone, and the reproduction of not only intermediate colors but also primary colors is inhibited.

The problem of transparency can be improved to some extent by reducing the particle size of the pigment particles to below the wavelength of light, that is, to the submicron level. However, it is difficult to pulverize pigments to submicron size, and the cost of coloring materials increases significantly. Furthermore, it is difficult to uniformly disperse pigments that have been pulverized to a submicron size in a resin, and as a practical matter, they exist as agglomerated aggregates to some extent in the resin, making it impossible to fully utilize the effect of pulverization. In view of this situation, the present inventors
As a result of intensive research to obtain a toner with excellent color reproducibility, especially as a color toner, the following invention was achieved.

[0005]

[Means for Solving the Problems] That is, the present invention provides C.
I. This is an electrophotographic toner characterized by containing a dye of DISPERSE BLUE 87 and/or a derivative thereof, and being colored with the dye.

The dyes used in the present invention are generally classified as disperse dyes or oil-soluble dyes. The content of the dye in the binder resin is not particularly limited, but is approximately 0.1 to 15.0, preferably 0.5 to 10.0, more preferably 1.0 to 6.0. It is about % by weight. Further, in order to adjust the hue, etc., other coloring materials may be used together.

In the present invention, C. I. DISPERS
A method for coloring a toner by incorporating a dye of E BLUE 87 and its derivatives into a toner is a so-called dispersion dyeing method in which the dye and resin particles are dispersed in an aqueous medium and treated at a predetermined temperature. This is the preferred method to use. As a method of applying the dye to an aqueous medium, a commercially available dye as a disperse dye may be used directly, but more preferably, when using an oil-soluble dye, the raw material of the dye (conch cake), An "aqueous dispersion of dye" obtained by mixing and pulverizing a dispersant and an aqueous medium using a ball mill, sand mill, shaker, etc. can be used. Known dispersants can be used as the dispersant, such as alkyl (benzene) sulfonates or sulfuric ester salts, naphthalene sulfonate condensates, polystyrene sulfonates,
Copolymers of styrene sulfonate and acrylic acid can be used. The processing temperature during dyeing is as follows:
Although it is difficult to make a general rule because it varies depending on the dye used, it is generally 15% from the glass transition point of the resin (meaning a toner precursor containing a resin or other components).
The range is up to 0°C. Dyeing may be carried out under pressure to increase the boiling point of water. In the present invention, it is particularly preferable to carry out the dyeing at a temperature approximately 40° C. higher than the glass transition point of the resin. The ratio of the aqueous medium during dyeing to the dispersed resin particles of the colored toner precursor is not particularly limited, but in order to increase the dyeing efficiency, the resin particles should be 20% by weight based on the entire aqueous dispersion.
It is preferable to set it as above.

[0008] The resin that is the main component of the particles in the present invention is not particularly limited, but styrene/acrylic resins, epoxy resins, polyester resins, etc. can be used. In the present invention, it is preferable that the toner binder resin is an ionic group-containing resin. In addition, from the viewpoint of adhesion to paper, fixability, transparency, etc., it is preferable to use a resin whose main component is a polyester resin consisting of a polyol and a polycarboxylic acid, and more preferably a polyester resin containing an ionic group. .

Ionic groups contained in resins such as polyester include carboxyl groups, sulfonic acid groups, sulfate groups,
Anionic groups such as phosphoric acid groups or salts thereof (hydrogen salts, metal salts), or cationic groups such as primary to tertiary amine groups, preferably carboxyl groups, carboxylic acid ammonium bases, Sulfonic acid group, sulfonic acid alkali metal base. Examples of sulfonic acid metal base-containing compounds that can be copolymerized with resin include sulfoterephthalic acid,
Examples include metal salts of 5-sulfoisophthalic acid, 4-sulfophthalic acid, 4-sulfonaphthalene-2,7dicarboxylic acid, and 5[4-sulfophenoxy]isophthalic acid. Metal salts include Li, Na, K, Mg, Ca, and C.
Examples include salts such as u, Fe, etc., and particularly preferred is Na salt. When the resin is a polyester resin, 5
-Preference is given to using sodium sulfoisophthalic acid. The content of these ionic groups is not particularly limited, but is approximately 0.02 to 0.5 equivalent/1000
A value within the range of g is appropriate.

The glass transition point of the resin used in the present invention is preferably 40°C or higher, more preferably 50°C or higher,
Furthermore, it is preferable that the temperature is 60°C or higher. When the glass transition point is lower than this, there is a tendency to aggregate during handling or storage, which may cause problems in storage stability. Furthermore, the softening point of the resin used in the present invention is 8
The temperature is preferably in the range of 0 to 150°C. Toners in which the softening temperature of the resin is kept lower than this tend to aggregate during handling or storage, and fluidity may deteriorate significantly, especially during long-term storage. If the softening point is higher than this, fixing performance will be impaired. Further, since it is necessary to heat the fixing roll to a high temperature, the material of the fixing roll and the material of the base material to be copied are limited. In the present invention, the average particle diameter D of the toner is 2.
It is preferable that it is 15 μm and 0.5 D to 2.0 μm.
It is preferable that particles with a particle size range of 0D account for 70% by weight or more of the whole, and particles with a sphericity of 0.8 or more account for 8% or more of the total weight.
It is preferable that substantially spherical particles account for 0 (number) % or more. If the particle shape, average particle diameter, and particle size distribution are not within the predetermined ranges, problems may occur in color image reproducibility, particularly in intermediate colors.

In the present invention, "resin particles obtained by wet-pulverizing a binder resin lump in the presence of a dispersant"
can also be used. As the dispersant used at this time, general known dispersants such as cationic, anionic, and nonionic dispersants can be used. In the present invention, it is preferable to use a compound having an alkali metal sulfonic acid base or the like. More preferably, condensates of naphthalene sulfonates, alkylbenzene sulfonates, polyacrylic acids, polystyrene sulfonates, copolymers of acrylic acid and styrene sulfonates, and the like can be used.

[0012] Toners obtained by the conventional method of mixing a pigment with a resin and pulverizing and classifying the resin have variations in the content and distribution of the pigment contained in each toner particle (exposed on the surface, near the surface, inside the particle). It is not possible to obtain a toner with uniform charging characteristics. In the toner obtained by the dispersion dyeing method of the present invention, the content of dye contained in each toner particle is uniform, and the distribution within the particle is also the same. Therefore, the resulting toner has very uniform charging characteristics. Now, in electrophotographic toners, a charge control agent is used to stabilize the charge. Charge control agents are usually colored, and many of them are problematic, especially when used in color toners. The dye used in the present invention not only has excellent hue, saturation, and light fastness as a process color, but also functions as a charge control agent to stabilize the triboelectric properties of the dyed resin. As a result of the above-mentioned effects, the toner of the present invention has uniform and highly stable charging characteristics with no variation among the individual particles constituting the toner, and also has excellent hue, saturation, and light fastness as a process color. It is thought that it will be excellent.

[0013]

[Examples] The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these in any way. In addition, the physical properties of the resin in Examples and Comparative Examples were measured by the following method.・Melting point, glass transition point A heating rate of 1 was measured using a differential scanning calorimeter (manufactured by Shimadzu Corporation).
Measurement was performed at 0°C/min. - Softening point was measured according to JIS K2351. - Number average molecular weight (vapor pressure method) Measured using a molecular weight measuring device (manufactured by Hitachi, Ltd.). (Synthesis of polyester resin) In an autoclave equipped with a thermometer and a stirrer, 815 parts by weight of dimethyl terephthalate, 320 parts by weight of dimethyl isophthalate, 491 parts by weight of ethylene glycol, 549 parts by weight of neopentyl glycol, and zinc acetate.
A transesterification reaction was carried out by charging 0.6 parts by weight and heating at 120 to 230°C for 120 minutes. Next, 40 parts by weight of 5-sodium sulfoisophthalic acid was added, and the
The reaction was continued at 30° C. for 60 minutes, and after the temperature was further raised to 250° C., the reaction was continued for 60 minutes at a system pressure of 1 to 10 mmHg to obtain a copolyester resin (A1). The molecular weight of the obtained copolymerized polyester resin (A1) was 2500, and the sulfonic acid metal base was 116 m equivalent/10
It was 00g. The amount of sulfonic acid metal base was determined by measuring the sulfur concentration in the copolyester resin. Also,
As a result of NMR analysis, the composition of the copolymerized polyester resin (A1) was found to be terephthalic acid as an acid component.
70.0MOL% isophthalic acid
27.5MOL% 5-sodium sulfoisophthalic acid 2.5MOL% Alcohol component: Ethylene glycol
48.0MOL% neopentyl glycol
It was 52.0 MOL%.

(Preparation of aqueous microdispersion) 34 parts by weight of the obtained copolymerized polyester resin (A1) and 10 parts by weight of butyl cellosolve were dissolved at 110°C, and then 5 parts by weight of water at 80°C were dissolved.
6 parts were added to obtain an aqueous microdispersion of copolyester resin having a particle size of about 0.1 μm. Furthermore, the obtained aqueous microdispersion was placed in a distillation flask, and the distillation temperature was 10
Distillation was carried out until the temperature reached 0°C, and after cooling, water was added to make the solid content concentration 38%. (B1) (Production of aqueous dispersion of resin particles 1) The resulting copolymerized polyester aqueous dispersion (B1) was placed in a four-necked 1-liter separable flask equipped with a coalescing granulation thermometer, a condenser, and a stirring blade. parts by weight (solid content 38% by weight), 8 parts by weight of acrylic acid/sodium styrene sulfonate copolymer (Toughtic AD [manufactured by Nippon Exlan Kogyo]),
The temperature was raised to 70°C while stirring. Next, add 26 parts by weight of deionized water containing 1.55 parts by weight of sodium chloride to 40 parts by weight.
The mixture was added dropwise over a period of minutes, and stirring was continued while maintaining the temperature at 70° C. for an additional 180 minutes. As a result, the copolymer with a submicron-order particle size that was present in the copolymerized polyester aqueous dispersion grew into particles, and the average particle size D became 6.3 μm and 0.
．． Occupancy of particles with particle diameters ranging from 5D to 2D 82
% by weight of polyester particles were obtained. The obtained polyester particles were thoroughly filtered and washed with deionized water to finally obtain an aqueous dispersion (C1) with a solid content concentration of 20% by weight. (Example 1)C. I. DISPERSE BLUE
87, dye conch cake was used, this conch cake was 20 parts by weight, dispersant Mignol 802 (manufactured by Ipposha Yushi Kogyo) 14 parts by weight, silicone antifoaming agent 0.1 part by weight,
Grinding and dispersion was carried out using a sand mill at a mixing ratio of 65.9 parts by weight of deionized water for about 3 hours to obtain a dye dispersion with an average particle size of 0.2 μm.

(Dyeing) An aqueous dispersion of the obtained resin particles (
C1) 100 parts by weight, dye (conch cake equivalent) 3
The weight part was placed in the styrene spot of the dyeing tester "Mini Color" manufactured by Texam Giken, and the temperature was raised from room temperature to 130 °C at a heating rate of 3 °C/min. After holding at 130 °C for 60 minutes, it was heated to room temperature. Upon cooling, dyed particles were obtained. The obtained dyed particles were filtered, washed, and dried with a spray dryer to obtain a colored toner. (Test) The obtained toner was fixed on paper using an electrophotographic method so that the average film thickness was 7 μm, and a sample for light resistance evaluation was prepared. Light resistance was evaluated using a fade meter, and the degree of discoloration after 20 hours of exposure to a carbon arc lamp (
Evaluation was made using the color difference ΔE) in the CIELAB coordinate system. A colorimeter CR-210 (manufactured by Minolta) was used to measure the chromaticity coordinates. Using the same obtained toner, a gradation image was copied onto a transparent film and observed and evaluated using an overhead projector. As a result, the hue was a clear greenish blue, the ΔE was 3, and the OHP (overhead project) image was extremely clear. Further, no particular problems were observed in the humidity dependence of charging properties, flow properties, insulation properties, fixing properties, sharp melt properties, anti-offset properties, etc.

(Comparative Example 1) As a dye, C.I. I. SOL
Example 1 except that VENT BLUE 35 was used.
It was carried out in the same way. The result was a clear blue with a greenish tinge, and ΔE was 16.

(Comparative Example 2) 95 parts by weight of the copolymerized polyester resin (A1) obtained in Example and (C.I.PIGMEN)
T BLUE 15:1) 5 parts by weight of a phthalocyanine cyan pigment were premixed in a ball mill and classified to obtain a colored toner having an average particle size of 7.4 μm. A test was conducted in the same manner as in Example 1 using this toner. The result was a clear blue with a greenish tinge, and ΔE was 1, but the OHP image was unclear.

50 parts by weight of the toner obtained in each of the Examples and Comparative Examples and 1000 parts by weight of ferrite carrier F-100 (manufactured by Powder Tech) were placed in a ball mill and stirred for about 15 minutes to form a developer. . Using the obtained developer, a continuous copying test of 10,000 sheets was conducted using an analog type copying machine having an amorphous silicon photosensitive drum. When the toner obtained in Example 1 was used, no significant difference was observed between the images at the beginning of the test and the images at the end of the test. Comparative example 1. In the toner obtained in 1, some "fading" was observed after 8,000 sheets were printed. Comparative example 2. 4000 for the toner obtained in
After 7,000 sheets, "fogging" occurred, and after 7,000 sheets, both "fogging" and "fading" increased, and the image quality deteriorated significantly. This is because toner particles with poor charging characteristics remain in the copying machine as the number of copies increases because the charging characteristics of individual toner particles vary and the amount of toner consumed is uneven.

[0019]

Effects of the Invention The toner for electrophotography according to the present invention can provide color images with good color tone and excellent color reproducibility and image retention, and is extremely stable in each particle constituting the toner. It was found that this material has unique charging characteristics.

Claims (1)

[Claims] [Claim 1] C. I. DISPERSE BLU
An electrophotographic toner characterized in that it is colored by containing a dye of E 87 and/or a derivative thereof.